Telephone system



July 11, 1933. J, B. DRAPER 1,917,879

TELEPHONE SYSTEM Original Filed Aug. 22, 1931A i /Nl/E/vTo/P q, I g 1 J. B. DRAPER BWM l Arrow/Ev sys-tenis. lts object is to improve and sinn.-

Patented `luly l1, 1933 Unirse stares PATENT einer JOHN B. nnnrnn, oir BitooiiLYii,.nEw YORK, Assreivon rro BELL TELEPHONE `LABO 4nn'roiains, iiiconionii'rnn, or iinw YORK, N. Y., A conroRAfrioN on NEW YORK Y,

TELEPHONE SYSTEM Application. lcd August 22, 1931, Serial No, 553,738; Renewed October 4, l1932.* Y

This invention relates to telephone systems and particularly to private branch exchange -plify the service over trunks incoming to systems of this kind. Y I

Systems have been proposed heretofore in which an operator in extending a connection from one exchange to another over a trunkv applies ringingcurrent to the trunk to cause.

a signal lamp to be lighted at the distant end of the trunk to call an operator thereat. Means are also employed whereby theV eX-A tiiiguisliing of this signal may `be delayed a ite interval after the operator has ceased applying the ringing current should the call remain unanswered.` Other systems have been used in which after a. connectionhas been established .over a trunk the call origi nating operator may recall the operator atv the distant end bymeans causing the lighting of the usual supervisory signal in the cord circuit of said operator connected at thedistant end of the trunk.

A feature of the present invention is an arrangement in a trunk circuit incoming to a private branch exchange for recalling the private branch exchange operator by the lighting of the trunk lamp at the private branch exchange in response to the application of ringing current by the operator at the distant end of the trunk and for delay! ing the extinguishing of said lamp a certain L llt" ii interval after said recalling ringing current" has been disconnected from lthe trunk.

. Another feature is the provision whereby the means for delaying the extinguishing of a trunk lanipafter the ringing ceases is made common to a plurality oftrunlrs.

This invention has been illustrated in the accompanying drawing in connection with a Vtrunk line T connecting a private branch ex*V I n l nections for lamp ,7 while? the sleeve, circuits change A and a central office B.

To illustrate the application of the invention in a circuit of this kind, descriptions Twill be made of a calloutgoing from' the private branch exchange A'and originating by' the insertion of the plug 1 of an ordinary private branch exchange operators cord, illustratcd in diagiamiiiatic form at 2, into. a

by a vdescription ofthe operations when a toll operator at the main exchange answers the call by inserting the'` plug 4 into a jack 5 of the trunk T. "llie-.pluglV istlie answering 'plug of a standard toll operators cordshown in diagrammatic form at6. Adescription will then be madel of the operations of the circuits when the operator at the privateV branch exchange-is rerung by theftoll operator and when the toll'operator is recalled bythe private branch exchange operator.

The private branchexchange operator may originate 'the outgoing call by inserting plug 1 into jack 3 ofan idle trunk. The idle condition is'indicated'by the lighted lamp 7 and all other corresponding lamps iii-.multiple therewith are associated with the multiple jacks of this trunk at other operators posi-V tions as willbe explained hereinafter. The circuit forthese lamps extends frombattery through the armature and back contact of` relay 8 through lanip7 vandl the other lamps to ground. Relay 9 is now operatedover the sleeve circuits from batteryjin the cord circuit 2 vthrough the sleeve terminals of plug 1 and jack 3 and winding of relay 9 to ground. A Relay 9 in operating establishes a partialv connectionfor lamp 10 to the frontcontact of the lower armature ofrelay 11, thev pur,- Y

Vconiiectediii multiple to batteryl., Itywill be explained hereinafter how relay Y13 is opi verated;V This relay, when operating, connectsv 100 en. 'i

the coi'iimoii battery 12 to the sleeve circuits of all other jacks through the corresponding lower armatures and baclr contacts of relays such as 9 to inale these jacks busy.

Relay 16 is also operated over the loop through the cord 2, tip and ring conductors of plug 1 and ack 3, the left-hand windings of repeating coil 17, windings of relay 16 to battery and ground. The operation of relay 16 closes an obvious circuit for the operation of relay 18. Relay 18 in operating closes a circuit for the operation of relay 19 from battery through the upper inner armature and frontkeontact of relay'18,fwinding of relay 19 to ground at the armature and bael Contact oif relay 20. VRelay 13 was also operated by the operation or" relay 18 from battery at the upper, inner armature and front contact of relay 18, winding of relay 13 to lguish it and connects this battery through this arinature and its-corresponding front` contact to the armature and back Contact to relay 21 which relay is associated with the next idle trunk line and vthereby causing the lamp ,corresponding to lamp-7 lin this trunk to be lighted to indieate to the operator the next trunk to select.- Tf this trunk is then taken forense/the lamp ofthe succeeding trunl'isnlighted and so forth until all. trunks are taken for use.

` Another circuit closed by the operation of relay18 is that for relay 23 as follows Frein battery7 upper inner armature and frontcontact of relay 18, upperV winding of relay 23,

. inalre-before-breal;V contact of relay 24 to ground,atrthearrnature and front Contact of relay 19. Relay 18 also reinoves battery and ground from the tipfand ring conductors of trunk T at the upper outer and lower outer armatures and corresponding back contacts and also connects battery through the wind-v ing of relay 25, lower outer armature and front contact of relay 18, one winding of retardation coil 27'to the ring conductor of the trunk. Relay V23 in operating n connects ground to the tip conductor through the Winding of relay 28, lower outer arinature and` front contact oit' relay 23 and the other winding of retardation coil 27'.v `With ground connected tothe tip conductor and batteries Awaitingon thisftrunk.A

28 are now operated and the'operati'on o.v

relay 23 closes at its upper and lower inner arinatures and front contacts atalking circuit through the condensers 32 and 33 roni the operator at 2 throughthe repeating coil 17 over the trunk T to the central oliice.

Thel toll operator at G now answers this call by inserting plug 4 into jack 5. This causes the polarized relay 29 by any ineans welll known inthe art to be disconnected from the tip and ring conductors to extinguish the lamp 30 and the tip and ring connections are extended through jack 5 and plug 4 and a bridge in the cord circuit at 6 to niaintaiurelays 28 and 25'operated. The operation of relay 28 closes a circuit for relay 24 freni battery, winding of this relay, arinature and front contact of relay 28 to ground 'at the armature and front Contact of relay. 19. Relay 28 in operating closes an obviousP locking circuit for relay 23 through its lower winding, while the operation of relay 24 opens the original energizing circuit ior relay 23 and extends the connection from ground at relay 19 to the front contact'biE the upper outer' armature ofrelay 11 the purpose of which will be explained hereinafter in connection with the rei-inging of the operator at the prii'iate'branch exchange A.

Torering or recall the private branch exchange operator the toll operator at 6 will operate the Aringing -key 37 to' apply ringing current over the trunk T to the private bran ch4 exchange; This causes the relays 25 and 28 to release immediately due to the opening orn the bridge in the cord circuit by the operation of the ringing key. The release of relay -28 causes the release of relay 23 to open the .talking circuit over the trunk, the purpose of this beingv to prevent clicks'or ringing induction freni beng heard at the calling station or by the operator at the private branch exchange. The ringing current applied by key 37 causes the operation of relay 39 and this relay in turn causes the operation of relay 2O from the ringing current in parallel'with relay 39. Relay 20 in operating opens the circuit orrelay 19 to causeA winding an d upper inner arinature and front contact over conductor 40 to' ground at the upper outer armature and back contact of relay 41 of the eoininon timing device 42.

This coinrnon tiiningdevice consists of a step-by-step switch 43 including a 'circulan terminal ban'l; and a brush therefor, a stepping. magnet. 44, of normal contacts 45 and release magnet 4G, This switch may be oit,V

any design Well known in the art. This dcvice also includes the relays 41,v 4 7 and 48 and interrupter 49 and may be as stated conunon to a plurality ci trunks such T by having the leads 40 and 50 multipled to these trunks. ,Relay 11 in operating closes a circuit for the lighting of lamp 1() 'trein battery through the lower armature and front contact oit relay 11 to lamp 10 to ground. This lamp, as stated, is associated with ack 3 and indicates tothe operator at this private branch exchange that the toll operator recalling. i

lVhen the toll operator releases the ringing key the relays 20 and 39. release. `Relay 2O in releasing causes the operationjoi' relay 19 and relay 19 in operating causes the operation of relayY 23. As relay 19 is slow in operating the operation of relay 23 is delayed to permit the bridge to beclosed across the tip and ringconductorsat the cord 6 when the key 37 is released, before the talking circuit is established. Relay 28 in reoperating after the operation of relay 23 locks relay as hereinbefore describedL and causesthc reoperation of relay 24, Relay 24 in operating establishes a connection to ground from the armature and front contact of relay 19- through its armature and Jfront contact, up-

per outer armatureand iront contact of relay 11, start conductor 50, lower inner armature y and back contact of relay 41, lower Winding of relay 47 to battery. This circuit causes the operation of relay 47 to start the timing device 42 to function to cause lamp 10 to remain lighted for a definite period after the toll operator has stopped ringing. Relay 47 in operating closes a locking circuitV for Vitself from battery through its upper Winding, ground at the upper armature and back contact of relay 41. Relay 47 also closes an obvious `interrupting circuit for relay 48 'from Y the interrupter49. This circuitcauses relay 48 to be alternately operated and releasedv to alternately open and close the obvious pulsing circuit for the stepping magnet 44. This alternate operation ofthe stepping magnet Will advance the brush of switch 43 until a connection is made from ground through the brush and a terminal of switch 43 through the Winding of relay 41 to battery. v When` this connection is made relay 41 operates and closes a locking circuit forl itself 'through the olil normal contacts 45 to ground to maintain itself operated until the switch has returned to normal. Relay 41 in operating opens the locking circuit for relays 47 and'll and opens the interrupting circuit for relay 48 and stepping magnet 44. Relay 41 also closes a circuit or the release magnet 46 to cause this magnet to return the sivitchto normal. Re-

upper armature and front contact tov -layll releasing at the end of thisperiod extinguishes lamp 10, which .has nowv been maintained:lighted, acer-tain period after the tollY operator released the key 37.

The private branch exchange operator may recall the toll operator by 'withdrawing and reinserting the lplug 1 into ackl `3. This causes relays 9,16, `18, 13, 19,23, 25, 28 and'` 24 to release and reoperate. The release andY reoperation of relays 18 and. 23v cause the usual supervisory lamp 1ny the trunk cord 6 to'tlash signifying to the toll operator that the private branch exchange operator is recalling. Y

Yi'hen the private branch exchange'operator releases the connection by removing plug 1 from jaclrl, relays 9, 16, 18, 13, `19, 23, 25, v Y 28 and 24 arereleas-ed. The release of relay 18' causesthe toll cord Vsupervisory lamp to light as a disconnect signalfand when the toll operator disconnects, the circuitsare restored to normah Whilethis inventionhas only been illustrat-ed in connection With one type ort' circuit,

it should be understood that it may readily be applied to other trunlrsystems `without de- Y parting from the spirit thereof and that'the present disclosure should merelybe 'consid-- connection of the cord circuit tothe trunk circuit and to the application et ringing current 'from said source to the trunk circuit y .tor actuating said signal, and ineens opera- L c r rot, the ringing current l maintaining said 'interval thereafter.

2. ln a telephone sys4 un, a trunk line, a

oord circuit, means toi' establishing connec-4 tion between said cord circuit and'said. trunk ie, a sie-ual in said trunk line',v a source of ringing current, means in said trunk line re'- e to ringing current from said source for actuating said signal, and means tor maintaining said signal actuatedttor a short connected.- Y

3. Tu v4a telephone system, a trunk circuit, a cord ci; 'it, a signalin said trunk circuit,

cuit for said fsignal, means responsive toline `connection 'or the cordA circuit to the u ci rit 'for par ly preparing the cirsource of ViiirnJiuQj curve to the `application of "ent from said source to the trunk c i. or completing the circuit for the sigand means for maintaining said signal iated a short interval. atterthe ringing` signal actuated a short val after the ringing current' is discurrent has been circuit, Y y ,A

il. In a telephone systenn a trunk circuit, a cord circuit, a signal in'said trunk circuit, an alternating current source, a relay in said trunk circuit responsive to alternating current, means responsive tothe connection of 'the cord circuit to thetrunk circuit and to removed from said trunk `rthe actuation of said relay .inI response to alternating current from said source or actuating said signal, and means responsive onl the release of saidv alternating current responsive relay forr maintainingsaid signal actuated 'for a short interval thereafter.

In a telephone system, trunk circuits, a cord circuit, a signal for each trunk circuit,

-a source of ringing current foreach trunk circuit, means responsive to the connection of the cord circuit. to a trunk circuit and to he application o-ringing current to said trunk circuit, from the associated source for actuating the corresponding signal, a timing device common to said trunk circuits, and means responsive on the cessation of the ringing current for maintaining saidsignal actuated a short interval thereafter under control ot' said common timing device;

6. In a telephone system, a trunk circuit, a cord circuit for connection to the trunk circuit` a signal in said trunk circuit, means operative after the cord circuit is connected to the trunk circuit for actuating said signal, and means operative after said first-mentioned means Vhas ceased to functionfor maintaining said signal actuated for a short interval thereafter.

7. In a telephone system, a trunk circuit,

a cord circuit forlconnection to the trunk circuit, a signal in said trunk circuit, means operative after the cord circuit is vconnected to the trunk circuit for actuating said signal,

said means is operating and a circuit closed by the operation of said. relay for controlling the signal, and means for maintain ing said relay operated a short interval after said inst-mentioned means has ceased to `t'unction to maintain said signal-actuated for said means including a relay actuated When 

